Dr. Nuthaporn Nuttayasakul

Consultant

Sahaviriya Steel Industries PLC

Background

Review of Current Specifications

Current Analyses

Continued Research and Testing

Conclusions

5

Develop Z purlin that suitable for long

span such as 12, 15 , 18 m

6

Orginated in 1946 based on Prof.

Winter at Cornell University

AISI 1946, 1956, 1960, 1962, 1968, 1980,

1986 ASD only

LRFD 1991, Combined ASD LRFD 1996

North American 2001, 2004, 2007, 2012,

2016

EIT 1024-53

AS/NZS, BS5950, Eurocode, Limit States

Review of 2016 AISI Specifications

Design Approach for Flexural Member

Failure Mode of Cold-Formed Section

• Effective Width Method traditionally addressed local

and global buckling. The distortional buckling

consideration were added in 2004

• Conceptualized the member as a collection of elements

and investigate local buckling of each element

separately

• Direct Strength Method (2004) incorporate all three

relevant buckling modes. And all buckling modes are

determined for the member as a whole

• Ensures that compatibility and equilibrium and

maintained at element junctures

Effective Width Method Vs

Direct Strength Method

Critical Stress

k = buckling coefficientt = member thicknessw = flat width

The plate

element will

continue to

carry load to

40% of the

initial elastic

value for a

square

stiffened

element

Effective Widths of Stiffened ElementsWeb and other Stiffened Elements under StressGradient

AISI Effective Widths of Uniformly Compressed Elements with a Simple Lip Edge Stiffener

Effective width design method

Direct Strength Method

Finite Strip Method

Flexural Members Having One Flange

Through-Fastened to Deck or

Sheathing (AISI I6.2.1)

• Tension Flange Attached to Deck or Sheathing

• Compression Flange Unbraced

• The bending capacity is less than fully braced

• But more than unbraced member

• Rotational stiffness by panel to purlin

connection

Restriction for using R-value

Properties Z Web Stiff Web Stiff2

LB (KN-m) 79.88 164.22 158.30

DB (KN-m) 75.90 67.71 73.01

LTB at 6 m (KN-m) 13.29 14.02 11.80

Weight(KN/m) 0.1235 0.1267 0.1267

LB (KN-m) 79.88 160.12 154.35

DB (KN-m) 75.90 66.02 71.19

LTB at 6 m (KN-m) 13.29 13.67 11.50

Normalize Value

Properties Z Web Stiff2 Web Stiff2 + Flange

LB (KN-m) 79.88 158.30 235.44

DB (KN-m) 75.90 73.01 78.04

LTB at 6 m (KN-m) 13.29 11.80 9.63

Weight(KN/m) 0.1235 0.1267 0.1327

LB (KN-m) 79.88 154.35 219.13

DB (KN-m) 75.90 71.19 72.64

LTB at 6 m (KN-m) 13.29 11.50 8.97

Normalize Value

Properties Z Web + Flange Web Stiff2 + Flange

LB (KN-m) 79.88 265.21 235.44

DB (KN-m) 75.90 66.83 78.04

LTB at 6 m (KN-m) 13.29 14.27 9.63

Weight(KN/m) 0.1235 0.1382 0.1327

LB (KN-m) 79.88 236.93 219.13

DB (KN-m) 75.90 59.70 72.64

LTB at 6 m (KN-m) 13.29 12.75 8.97

Normalize Value

Determine the optimal geometry and manufacturing possibility

Deflection Control during installation

Finite Element Study Full Scale Static Load Testing Wind Chamber Testing for uniform

gravity and wind uplift

Long Span Z purlin calculations and analyses were done on various cross sections

Trends and Findings will be used to determine the optimal cross section

The full scale test will be used confirm the analyses